This invention is generally concerned with an angiographic collimator for removing unwanted divergent beams of radiation received from a radionuclide source, leaving a well resolved radiation beam for detection and analysis of a patient's cardiac system. More particularly, the invention is directed to an angiographic collimator having a layered wall structure for removing not only unwanted angularly divergent gamma radiation beams, but also for removing gamma radiation inelastically scattered by the collimator structure itself enabling improved analysis of a patient's cardiac system.
Angiographic imaging methods and apparatus are undergoing rapid evolution as efforts are being made to improve the ability to image selected internal portions of the human cardiac system. The effectiveness of these various imaging methodologies, and even the ability to use certain imaging techniques for effective clinical diagnosis of the cardiac system, depends primarily on spatial resolution and on the associated signal to noise ratio in the data being accumulated. Present angiographic technology is able to generate in a manner safe to a patient, a gamma radiation intensity adequate to image a number of abnormalities in the heart and the associated cardiac system. However, current technology cannot effectively collimate this gamma radiation intensity without counting certain divergent radiation and thus including substantial unwanted noise in the resulting data. Such divergent, unwanted signal derives, for example, from radiation which has been inelastically scattered from the collimator structure itself. This deficiency therefore requires exposing the patient to larger intensities of gamma radiation in order to achieve a desired resolution. Unfortunately, such increased radiation exposure can increase the hazard to a patient, and moreover there are some divergent radiation sources whose deleterious effects cannot be alleviated even by increasing the radiation signal level from the patient.
It is therefore an object of the invention to provide an improved method of manufacture and method for collimation of radionuclide radiation in an angiographic inspection system.
It is another object of the invention to provide a new method of manufacture of an angiographic collimator for a gamma ray beam.
It is a further object of the invention to provide an improved angiographic collimating device for removing divergent gamma radiation and X-ray beams received from, or passed through, a patient undergoing cardiac system analysis.
It is an additional object of the invention to provide a new angiographic gamma ray collimator assembly for providing highly resolved, high intensity data characteristic of a patient but without having to increase patient exposure to gamma radiation.
It is yet another object of the invention to provide an improved angiographic radiation collimator assembly having a layered wall material structure for substantially reducing inelastic scattered X-rays present in the detected data signal.
It is still a further object of the invention to provide a new radionuclide gamma ray collimator having a lead base structure with an outer layer of a material which preferentially absorbs X-rays generated from inelastic scattering of gamma rays from the lead base collimator structure.
It is yet an additional object of the invention to provide an angiographic radiation collimator having a selectable collimator length using a stack of different predetermined height collimator units.
It is still a further object of the invention to provide an angiographic gamma ray collimator of lead with a thin tin layer on the collimator walls to absorb lead X-rays generated by inelastic gamma ray scattering from the lead collimator.
Other objects, features and advantages of the present invention will be readily apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings described below wherein like elements have like numerals throughout the several views.